In recent years, in order to achieve a higher speed and a larger capacity in wireless communications performed in wireless communication systems such as a mobile telephone system, some discussions about next-generation wireless communication technologies have been made. For example, a technology has been discussed about establishing a communication using a carrier in a frequency band that requires a license (licensed band carrier (LC)) and a carrier in a frequency band that does not require a license (unlicensed band carrier (UC)) in a communication standard referred to as long term evolution (LTE). This technology is referred to as licensed assisted access (LAA).
In the LAA, when a terminal performs an up Link (UL) transmission to a base station in an unlicensed band, the base station transmits a UL grant, which requests transmission of data, to the terminal via a licensed band. Further, for example, the base station performs listen before talk (LBT) in the unlicensed band before the terminal performs the UL transmission. Furthermore, for example, there have been discussions to cause the base station, upon detecting that the unlicensed band is idle, to transmit a reservation signal in the unlicensed band until a timing of the UL transmission performed by the terminal, in order to reserve the unlicensed band used by the terminal for the UL transmission. This allows the terminal to perform the UL transmission by using the unlicensed band a predetermined time after the UL grant. Prior art example is disclosed in 3GPP RAN1 Contribution document R1-150186.
Incidentally, in the technology disclosed in the above-referenced Non Patent Literature, if a busy state of the unlicensed band is continued and the terminal does not receive the reservation signal in the unlicensed band until the timing of the UL transmission, the terminal cancels the UL transmission, for example. Accordingly, the opportunity of transmitting data scheduled to be transmitted by the UL transmission is suspended until a predetermined period elapses after a next UL grant transmitted from the base station. Therefore, in some cases, a throughput of data transmission in an uplink from the terminal to the base station may be reduced.